This invention relates to an apparatus for connecting flanged pipes, particularly large diameter flanged pipes which in use are subject to high pressure such as risers in oil-field applications.
It is a well-known requirement that shorter sections of pipe such as riser sections must be joined together to form longer pipes or risers. Such pipe sections are provided in standard lengths and delivered to the location in which the pipe is to be installed. Each section has a circular flange at each end, each flange being provided with a number of apertures and a circumferential groove in the mating surface of the flange, in which may be placed a ring seal. Two pipe sections are brought together such that the mating surfaces are aligned with a ring seal between them. Threaded fasteners or bolts are placed in the apertures and nuts are tightened onto the bolts. The nuts are tightened to a predetermined torque in order to energise the ring seal.
The known method of joining flanged riser sections suffers from the disadvantage that it is slow and difficult to carry out under adverse conditions. The method requires considerable strength, skill and reliability of operators, together with the use of heavy tools in confined spaces or areas of difficult access. Furthermore, the securing force is dependent on the extent of wear and the general condition of the threaded fasteners.
JP 0800-11063 discloses an auxiliary device for tightening the nuts and bolts that fasten the flanges of pipe sections. A piston portion of the device is attached to each of the bolts and hydraulic pressure is applied to the piston head which draws each bolt towards the device allowing the associated nut to be manually tightened. However, time and effort is required to attach each piston portion of the device to, and remove the portion from, each individual bolt for tightening the associated nut.
According to a first aspect of the invention, there is provided an apparatus for connecting two flanged pipes comprising at least one piston arrangement having a pair of opposed pistons slidable within a hydraulic cylinder,                each of said pair of pistons having a rod extending therefrom and adapted to receive a fastener at its end remote from the piston,        each of said rods extending through an aperture at the respective cylinder end and being adapted to pass through a respective aperture in the flange of a flanged pipe,        each of said pistons having an associated biasing means which urges the piston away from its respective cylinder end,        wherein pressurisation of hydraulic fluid in the cylinder causes the piston to move towards its respective cylinder end against the urging action of the biasing means.        
In use the apparatus may be placed between two flanged pipes such that the two opposing rods of the piston arrangement extend through the respective apertures in the flanges of the two flanged pipes. Nuts are secured to threaded ends of the rods, so that the apparatus is securely held between the two flanged pipes. When the hydraulic fluid is pressurised the pistons are forced against the biasing action so that the rods and nuts move outwards. The nuts may then be further tightened onto the threaded ends of the rods. When the pressure in the hydraulic fluid is removed the biasing means urges the pistons towards each other, so energising the connection between each flanged pipe and the apparatus.
Preferably the fastener is a threaded fastener. Preferably, the apparatus comprises a cylindrical body. Preferably, the cylindrical body has an axial through bore. This bore is preferably the same size as the internal bore of the two pipe sections to be joined. When the apparatus is used to join two pipe sections, the axial through bore is aligned with the internal bore of each of the pipe sections.
Preferably, the apparatus comprises a plurality of said piston arrangements spaced at intervals about and externally of the through bore. Preferably, there are four or more piston arrangements spaced equidistantly on a circumference. Preferably, the piston arrangements are arranged such that the pistons move parallel to the axis of the through bore. A standard flange has 12 apertures, so the apparatus for joining pipes having such flanges would have 12 piston arrangements arranged at the same relative positions as the 12 apertures.
Preferably, each of the biasing means comprises a spring. The spring may be arranged around the rod and may act between the piston and the respective end wall of the cylinder. Typically the spring comprises a number of conical washers, although a helical spring of appropriate stiffness may be used.
Preferably, hydraulic fluid is provided between the pistons in the cylinder. Preferably, the apparatus comprises one or more hydraulic fluid passages communicating with the one or more hydraulic cylinders at a connection point in each of the cylinders arranged between the two pistons.
Preferably the apparatus comprises first and second bearing faces at opposite ends adapted to bear in use against the end faces of the pipes to be joined. Preferably each of the bearing faces is provided with a circumferential groove adapted to house a ring seal.
According to a second aspect of the invention, there is provided a pipe connection comprising a first pipe having a first flange at the end thereof, a second pipe having a second flange at the end thereof, and an apparatus according to the first aspect of the present invention.
Preferably, the two opposing rods of the piston arrangement extend through respective apertures in the flanges of the two pipes.
Preferably, the pipe connection further comprises a threaded fastener secured to the end of each of the rods. Preferably, the end of each rod is provided with an external thread and the threaded fastener is a nut.
Preferably, the number of piston arrangements is equal to the number of apertures in each flange.
According to a third aspect of the invention, there is provided a method for connecting first and second flanged pipes, the method comprising the steps of:                (a) providing an apparatus comprising at least one piston arrangement having first and second opposed pistons slidable within a hydraulic cylinder, each of said first and second pistons having a rod extending therefrom and having associated biasing means adapted to bias the piston away from the end of the cylinder;        (b) placing the apparatus between the opposing flanges of the flanged pipes such that the rod of the first piston projects through an aperture in the flange of the first pipe and the rod of the second piston projects through an aperture in the flange of the second pipe;        (c) securing a fastener to each of the rods and tightening the fastener against the respective flange;        (d) pressurising the cylinder between the pistons to cause the pistons and rods to move away from each other and to cause the fasteners to move away from the respective flanges;        (e) tightening further each fastener against the respective flange; and        (f) reducing the pressure in the cylinder to cause the pistons and rods to move towards each other under the action of the biasing means and to cause the fasteners to apply a greater clamping force to the respective flanges.        
Preferably the or each fastener is a threaded fastener.
Steps (d) to (f) may be repeated as required, particularly in the case when a seal ring is provided between the apparatus and each of the flanges, and the seal ring deforms plastically under the action of the increased clamping force.
The method may further include the step of measurement of the clamping force. The force may be measured using at least one tension indicator connected to the or each fastener. Alternatively, the force may be measured using at least one load washer.
Preferably the apparatus is an apparatus according to the first aspect of the invention.
According to a fourth aspect of the invention, there is provided an apparatus for connecting a first pipe having a flange and a second pipe comprising at least one piston arrangement having a piston slidable within a hydraulic cylinder,                the piston having a rod extending therefrom and adapted to receive a fastener at its end remote from the piston,        said rod extending through an aperture at the respective cylinder end and being adapted to pass through a respective aperture in the flange of the first flanged pipe,        said piston having an associated biasing means which urges the piston away from its respective cylinder end,        wherein pressurisation of hydraulic fluid in the cylinder causes the piston to move towards its respective cylinder end against the urging action of the biasing means.        
Preferably the apparatus further comprises a flange remote from said rod for abutting a flange provided on the second flanged pipe. Preferably the flange of the apparatus has at least one aperture for receiving one or more fasteners. Alternatively the apparatus further comprises a weld neck remote from said rod for welding of the apparatus to the second flanged pipe. Alternatively the apparatus forms an integral part of the inlet of an item of equipment.
According to a fifth aspect of the invention, there is provided a method for connecting a first pipe having a flange and a second pipe, the method comprising the steps of:                (a) providing an apparatus comprising at least one piston arrangement having a piston slidable within a hydraulic cylinder, said piston having a rod extending therefrom and having associated biasing means adapted to bias the piston away from the end of the cylinder;        (b) placing the apparatus between the pipes such that the rod of the piston projects through an aperture in the flange of the first pipe;        (c) securing a fastener to the or each rod and tightening the fastener against the flange of the first pipe;        (d) pressurising the cylinder between the or each piston to cause the or each piston and rod to move away from each other and to cause the or each fastener to move away from the flange of the first pipe;        (e) tightening further the or each fastener against the flange of the first pipe; and        (f) reducing the pressure in the cylinder to cause the or each piston and rod to move towards each other under the action of the biasing means and to cause the or each fastener to apply a greater clamping force to the flange of the first pipe.        
Preferably the apparatus further comprises a flange remote from said rod and having at least one aperture, the second pipe is provided with a flange having at least one aperture, and the method further comprises the step of locating a bolt through the or each aperture of the flange of the apparatus and the or each aperture of the flange of the second pipe, securing a fastener to the or each bolt and tightening the or each fastener.
Alternatively the apparatus further comprises a weld neck remote from said rod, and the method further comprises the step of welding the apparatus to the second pipe.
Example embodiments of the invention will now be described by way example only, with reference to the accompanying Figures, in which:—